The present invention relates to valves, and more particularly, to fuel tank vent valves.
Fuel tank xe2x80x9cvent valvesxe2x80x9d are commonly incorporated in vehicle fuel systems for the purposes of allowing air to displace the fuel as it is consumed, and for releasing vapor or gaseous pressure buildup in the fuel tank. The main objective for most vent valves is to allow the flow of gases in or out of the tank, while preventing any liquid fuel from escaping, regardless of the angle of orientation of the vehicle. Venting is commonly required because vapor is returned to the fuel tank from many types of engines during operation, and this vapor must be vented to avoid pressurizing the tank. This vapor must be conducted through a vapor outlet in the vent. Thus, vent valves must be designed to close their vapor outlets during certain operating conditions, such as vehicle tilting, sloshing of fuel when the tank is full or near-full, or roll-over of the vehicle, in order to prevent spillage of liquid fuel through the vapor outlet.
Presently known vent valves close the vapor outlet through the use of a float. If the vent Valve were to close due to a condition, such as sloshing in the tank, there is a commonly encountered problem in reopening the closed vent valve because the vapor from the engine creates pressure within the fuel system which applies forces against the seat which in turn must be overcome to reopen the vent valve. In this particular situation, the pressure in the fuel tank exerts enough force over the area of the valve outlet that the vent valve cannot easily reopen upon the return of the vehicle to normal operating conditions. As a result, most vent valves are designed to have a small sized vapor outlet so that the forces applied by the fuel vapor pressure against the small area of the outlet can then be easily overcome by the proper sizing and weighting of the float.
However, in fuel systems where high vapor flow rates are required, a vent valve having a small vapor outlet is inadequate to fully relieve the pressure. Therefore, these vent valves are: designed with a larger vapor outlet to provide for adequate flow rates for fuel systems with high gaseous return flow from the engine. However, this compromises the ability of the float to re-open the vapor outlet if it closes for any reason and the tank subsequently pressurizes. Thus, there is a need in the fuel distribution system industry for a vent valve to have a sufficiently large vapor outlet to provide adequate discharge flow rates, while still being able to reopen the vent valve during tank pressurized conditions.
In accordance with aspects of the present invention, a vent valve includes a valve body defining an inner cavity and having an inlet for admitting a fluid or a gas into the cavity and an outlet port for discharging the fluid or the gas from the cavity to the exterior of the valve body. The vent valve also includes a main vapor outlet disposed in the valve body and in fluid communication with the outlet port and the inlet. A valve mechanism is provided and is positioned within the inner cavity. The valve mechanism is movable between a first position, wherein the main vapor outlet is closed, and a second position, wherein the main vapor outlet is open.
In accordance with one aspect of the present invention, the valve mechanism of the vent valve includes a valve member or poppet having a seating surface for mating with the main vapor outlet in a leak-proof manner. The poppet has a longitudinal bore extending therethrough and is disposed in fluid communication with the main vapor outlet, thereby defining an auxiliary vapor outlet. The auxiliary vapor outlet has a smaller cross-sectional area than the main vapor outlet. The valve mechanism also includes a buoyancy member having a seating surface for mating with the auxiliary vapor outlet in a leak-proof manner, and a poppet retaining member supported by a portion of the buoyancy member. The retaining member is operable to retain the poppet in a slidably engageable manner. The retaining member has a slot in communication with the inner cavity and the auxiliary vapor outlet. The buoyancy member is operable to translate relative to the poppet from a first auxiliary vapor outlet closed position, wherein the surface of the buoyancy member is seated into the auxiliary vapor outlet, to an auxiliary outlet opening position, wherein the seating surface of the buoyancy member unseats from the auxiliary vapor outlet.
In accordance with another embodiment of the present invention, the vent valve includes a cup seat biased into sealing engagement with an interior portion of the valve body. The cup seat includes a main vapor outlet in fluid communication with the outlet port and the inlet.